Gary Bañuelos

Phytoremediation of Contaminated Soil and Water

Field Demonstrations of Phytoremediation of Lead Contaminated Soils Phytoremediation by Constructed Wetlands Factors Influencing Field Phytoremediations of Selenium-Laden Soils Phytoremediation of Selenium-Polluted Soils and Waters by Phytovolitization Metal Hyperaccumulator Plants: a Review of the Ecology and Physiology of a Biological Resource For Phytoremediation Of Metal-Polluted Soils - Potential for Phytoextraction of Zinc and Cadmium from Soils Using Hyperaccumulator Plants Improving Metal Hyperaccumulator Wild Plants to Develop Commercial Phytoextraction Systems: Approach and Progress Physiology of Zn Hyperaccumulation in Thlaspi caerulescens Metal-Specific Patterns of Tolerance, Uptake, and Transport of Heavy Metals in Hyperaccumulating and Non-Hyperaccumulating Metallophytes The Role of Root Exudates in Nickel Hyperaccumulation and Tolerance in Accumulator and Nonaccumulator Species of Thlaspi Engineered Phytoremediation of Mercury Pollution in Soil and Water Using Bacterial Genes Metal Tolerance in Plants: The Role of Phytochelatins and Metallothioneins The Genetics of Metal Tolerance and Accumulation in Higher Plants Ecological Genetics and the Evolution of Trace Element Hyperaccumulation in Plants The Role of Bacteria in the Phytoremediation of Heavy Metals Microphyte-Mediated Biogeochemistry and Its Role in In Situ Selenium Bioremediation In Situ Gentle Remediation Measures For Heavy Metal Polluted Soils In Situ Metal Immobilization and Phytostabilization of Contaminated Soils Phytoextraction or In-Place Inactivation (Phytostabilization): Technical, Economic, and Regulatory Considerations of the Soil-Lead Issue NTI/Sales Copy

The phytomanagement of trace elements in soil.

Trace elements (TEs) occur at low concentrations (<1000 mg kg −1) in organisms, yet they have a large biological effect, both as essential nutrients and environmental contaminants. Phytomanagement describes the manipulation of soil-plant systems to affect the fluxes of TEs in the environment with the goal of remediating contaminated soils, recovering valuable metals, or increasing micronutrient concentrations in crops. Phytomanagement includes all biological, chemical, and physical technologies employed on a vegetated site. Successful phytomanagement should either cost less than other remediation or fortification technologies, or be a profitable operation, by producing valuable plant biomass products. This may include bioenergy or timber production on contaminated land, a practice that does not reduce food production. We review the components of phytomanagement and the underlying biogeochemical processes, with a view to elucidating situations where this technology may be successfully applied and identifying future research needs. Many full-scale operations have proved the efficacy of plants to reduce contaminant mobility in soils (phytostabilization), particularly when used in combination with other technologies. As a stand-alone technology, the oft-touted use of plants to extract TEs from contaminated soils (phytoextraction) or low-grade ore bodies (phytomining) is unsuitable for most, if not all, sites due to low-extraction rates and problems caused by site heterogeneity, the limited rooting depth of plants and the presence of contaminant mixtures. Unsubstantiated claims about phytoextraction have tarnished the reputation of all “phyto” technologies. Nevertheless, phytoextraction, as part of a larger environmental toolkit, has a role in phytomanagement. The growth, or lack thereof, of profitable companies that provide phytomanagement will indicate its value. A critical knowledge gap in phytomanagement is the integration of the processes that affect plant–TE interactions and the biophysical processes affecting TE fluxes in the root zone, especially the effect of roots on contaminant fluxes.

Selenium Cycling Across Soil-Plant-Atmosphere Interfaces: A Critical Review

Selenium (Se) is an essential element for humans and animals, which occurs ubiquitously in the environment. It is present in trace amounts in both organic and inorganic forms in marine and freshwater systems, soils, biomass and in the atmosphere. Low Se levels in certain terrestrial environments have resulted in Se deficiency in humans, while elevated Se levels in waters and soils can be toxic and result in the death of aquatic wildlife and other animals. Human dietary Se intake is largely governed by Se concentrations in plants, which are controlled by root uptake of Se as a function of soil Se concentrations, speciation and bioavailability. In addition, plants and microorganisms can biomethylate Se, which can result in a loss of Se to the atmosphere. The mobilization of Se across soil-plant-atmosphere interfaces is thus of crucial importance for human Se status. This review gives an overview of current knowledge on Se cycling with a specific focus on soil-plant-atmosphere interfaces. Sources, speciation and mobility of Se in soils and plants will be discussed as well as Se hyperaccumulation by plants, biofortification and biomethylation. Future research on Se cycling in the environment is essential to minimize the adverse health effects associated with unsafe environmental Se levels.

Vegetative production of kenaf and canola under irrigation in central California

Abstract Kenaf (Hibiscus cannabinus L.) and canola (Brassica napus L.) are potential alternative crops for forage production and phytoremediation adaptable to irrigated agriculture in central California. However, little information is available on the water requirements for growing these crops under irrigated conditions, particularly with regard to increasing their vegetative growth. A 3-year field study was undertaken to evaluate kenaf (cultivars: 7-N, Everglades-41, Tainung-2 and breeding lines: C-531, C-533) and one variety of canola (Westar) for potential cultivation. Kenaf was grown as a spring crop and canola was grown as a fall crop. Plants were irrigated at five different levels, ranging from 368 to 1413 mm for kenaf and from 62 to 359 mm for canola per growing season. For kenaf, shoot and root dry matter (DM) production increased as irrigation was increased incrementally from 25 to 125% crop evapotranspiration (Etc); water application at 150% Etc had no increased benefit. Bark:core ratio of the various kenaf cultivars, however, was unaffected by the level of irrigation. For canola, shoot DM and leaf:stem ratio increased with irrigation up to 125% Etc, whereas root DM did not differ significantly among irrigation treatments. Kenaf produced at least twice as much biomass as canola and both crops produced maximum vegetative yields at 100–125% Etc in central California.

Trace elements in soils and plants: An overview

Abstract The movement of both essential and non‐essential trace elements through agricultural ecosystems and food chains is a complex phenomenon. Such elements as As, B, Cd, Cr, Cu, Hg, Ni, Pb, Se, U, V, and Zn, are generally present in soils in low concentrations but concentrations may be elevated because of natural processes and human activities, such as fossil fuel combustion, mining, smelting, sludge amendment to soil, fertilizer application, and agricultural practices. Although a significant effort has been expended over the past 40 years to evaluate and quantify the transfer of trace elements from soils to plants, more attention needs to be given to mechanisms within the soil and plant systems, which influence their solubility, chemical speciation, mobility, and uptake by and transport in plants. The prediction of movement of trace elements in the agricultural ecosystem must be partially based on understanding the soil and plant processes governing chemical form and the uptake and behavior of trace ...

Selenium accumulation in selected vegetables

Absract Greenhouse experiments were conducted to determine selenium (Se) uptake by sulfur‐accumulating vegetables. Cabbage (Brassica oleracea var. capitata), broccoli (Brassica oleracea var. botrytis), Swiss chard (Beta vulgaris var. cicla) and collards (Brassica Oleracea var. acephda) were grown in a soil mix to which 4.5 mg of selenate or selenite had been added per kg of soil. Plants were grown to maturity, separated into plant organs, and the tissues analyzed for Se and sulfate (SO4). Vegetables grown in selenate laden soil significantly (P<0.05) accumulated higher concentrations of Se than plants grown in selenite laden soil. The highest concentrations of Se and SO4 were found in the broccoli floret and vegetable leaf tissues. A second greenhouse experiment examined the uptake of Se and SO4 in broccoli (Brassica oleracea var. botrytis) grown hydroponically with increasing Se concentrations. Treatments consisted of three Se concentrations (2, 6, and 15 mg of selenate, added as Na2SeO4/L to a synthetic...

Phytoextraction and Accumulation of Boron and Selenium by Poplar (Populus) Hybrid Clones

ABSTRACT There has been much interest recently in central California for reusing drainage water to grow trees. A sand-culture study was conducted to investigate the accumulation of boron (B) and selenium (Se) in eight hybrid poplar (Populus) clones irrigated with synthetic agricultural effluent containing increasing levels of chloride salt, B, and Se. Electrical conductivity (EC) ranged from 1.5 to 15 dS m-1, B levels from 1 to 5 mg L-1, and Se levels from 100 to 500 μg L-1. Compared with all tree organs, the leaves accumulated the greatest concentrations of B and Se at the time of harvest. The results show that pooled leaf B concentrations were positively correlated with EC levels (r = 0.78, P < 0.001) and negatively correlated (r = -0.53, P < 0.001) with leaf dry matter for all clones at all tested B levels. Combined leaf and stem Se data show, respectively, a significant decrease (P < 0.05 level) in tissue accumulation of Se with increased salinity. Toxicity symptoms (e.g., burning leaf margins, shoot ...

Evaluation of Atriplex lines for selenium accumulation, salt tolerance and suitability for a key agricultural insect pest.

Thirty Atriplex lines were examined for potential habitat improvement and phytoremediation of selenium (Se) contaminated sites. Studies were conducted to determine the biomass production, Se accumulation, and resistance of each line to the beet armyworm, Spodoptera exigua, an agriculturally important insect. Plants were tested using three salinity treatments: (1) control, no Se; (2) NaCl and CaCl2 salts and 1 mg l(-1) Se (12.7 microM) added as sodium selenate; and (3) iso-osmotic to treatment 2 containing high concentrations of sulfate and I mg l(-1) Se added as sodium selenate. Insect bioassays measured survival, growth, and development. Atriplex patula. A. spongiosa 415862, A. hortensis, A. hortensis 379088 and A. hortensis 379092 were among the top biomass producers and Se accumulators, yet they exhibited significantly reduced insect growth, development, and survival. High background sulfate strongly reduced Se accumulation, suggesting that phytoremediation potential is greatest in saline areas having low to moderate sulfate levels. However, these lines grew well in high salinity soils, indicating possible use as a self-seeding cover crop to improve habitat. All plant lines grown in control and high sulfate salinity treatments are acceptable oviposition sites for S. exigua, indicating that these plants would help reduce populations of this key agricultural pest.

Selenium Accumulation, Distribution, and Speciation in Spineless Prickly Pear Cactus: A Drought- and Salt-Tolerant, Selenium-Enriched Nutraceutical Fruit Crop for Biofortified Foods

The organ-specific accumulation, spatial distribution, and chemical speciation of selenium (Se) were previously unknown for any species of cactus. We investigated Se in Opuntia ficus-indica using inductively coupled plasma mass spectrometry, microfocused x-ray fluorescence elemental and chemical mapping (μXRF), Se K-edge x-ray absorption near-edge structure (XANES) spectroscopy, and liquid chromatography-mass spectrometry (LC-MS). μXRF showed Se concentrated inside small conic, vestigial leaves (cladode tips), the cladode vasculature, and the seed embryos. Se K-edge XANES demonstrated that approximately 96% of total Se in cladode, fruit juice, fruit pulp, and seed is carbon-Se-carbon (C-Se-C). Micro and bulk XANES analysis showed that cladode tips contained both selenate and C-Se-C forms. Inductively coupled plasma mass spectrometry quantification of Se in high-performance liquid chromatography fractions followed by LC-MS structural identification showed selenocystathionine-to-selenomethionine (SeMet) ratios of 75:25, 71:29, and 32:68, respectively in cladode, fruit, and seed. Enzymatic digestions and subsequent analysis confirmed that Se was mainly present in a “free” nonproteinaceous form inside cladode and fruit, while in the seed, Se was incorporated into proteins associated with lipids. μXRF chemical mapping illuminated the specific location of Se reduction and assimilation from selenate accumulated in the cladode tips into the two LC-MS-identified C-Se-C forms before they were transported into the cladode mesophyll. We conclude that Opuntia is a secondary Se-accumulating plant whose fruit and cladode contain mostly free selenocystathionine and SeMet, while seeds contain mainly SeMet in protein. When eaten, the organic Se forms in Opuntia fruit, cladode, and seed may improve health, increase Se mineral nutrition, and help prevent multiple human cancers.

Biotransfer Possibilities of Selenium from Plants Used in Phytoremediation

ABSTRACT We are investigating the biotransfer of accumulated Se by the plant in several phytoremediation systems. In study I, we evaluated the biotransfer of Se from Indian mustard, a Brassica species, to the insect-cabbage looper (Trichoplusia ni); mortality, deterrence, and biomagnification of Se were examined. We determined that feeding behavior of food chain consumers was affected not only by the plant concentration of Se, but also by the mobility of the insects and choice of feed available. In study II, we examined the survival and development of beet army worm (Spodoptera exigua) fed Se-enriched plant tissues from different lines of saltbush (Atriplex spp.) After feeding on lines of saltbush that produced high biomass and accumulated high concentrations of Se, insect growth and survival was reduced. In studies III, IV, and V, lambs, dairy cows, and rabbits were fed Se-enriched Brassica and Medicago (alfalfa) plants as part of their feed ration. None of the tested animals exhibited any Se toxicity symptoms, but they had increased levels of Se in most tissues sampled (e.g., organs, blood, urine, feces), excluding milk. In study VI, we evaluated biotransfer of Se from broccoli to rats to determine efficacy of Se for reducing colon cancer. We found that Se-enriched plant material was more effective than inorganic sources of Se for preventing precancerous colon lesions. Results from all studies clearly show that Se absorbed by plants can be transferred biologically in an intentional or unintentional manner to insects and animals.